1. Field of the Invention
The invention relates to an offset rubber-blanket sleeve for a non-grooved rubber-blanket cylinder for applying a printed image to material in the form of sheets or webs.
2. Description of the Related Art
In offset rotary printing machines, rubber blankets are conventionally held on the rubber-blanket cylinder by mechanical fastenings. Such a rubber-blanket cylinder has an axially extending groove with clamping segments in which the opposite ends of the rubber blanket are fastened. In such a clamping mechanism, a clamping groove is formed in the body of the rubber-blanket cylinder and extends axially in segments along the width of the cylinder. This clamping groove forms an interruption in the cylindrical outer surface area of the rubber-blanket cylinder so that a pressure-free or print-free zone occurs during the rolling movements of the rubber-blanket cylinder. Because of the groove, bending vibrations are induced in the cylinders which roll on one another. This has a negative impact on printing quality.
To overcome these difficulties, rubber-blanket sleeves for a rubber-blanket cylinder without a cylinder groove have already been developed. For example, a rubber-blanket sleeve is known from the German Patent 27 00 118 C2 in which a continuous coating of elastic material, preferably rubber, is arranged on an exchangeable carrier or support sleeve of plastic or metallic material. The rubber coating is applied to the support sleeve so as to be completely free of gaps and seams. The rubber-blanket sleeve produced in this way is then slid over the rubber-blanket cylinder by means of compressed air and fixed thereon by cutting off the air supply.
In order that the rubber-blanket sleeve remains fixed in a stationary manner on the rubber-blanket cylinder during the printing process, this rubber-blanket sleeve is under-dimensioned and is widened by placement on the rubber-blanket cylinder so that the rubber-blanket sleeve is held by the joining pressure between the outer surface area of the rubber-blanket cylinder and the inside of the sleeve. The rubber-blanket sleeve must therefore be capable of absorbing considerable peripheral or circumferential forces. For this reason, the known rubber-blanket sleeve is constructed from a support sleeve having a high modulus of elasticity and a compressible rubber coating which cannot by itself absorb the high circumferential forces.
Nevertheless, such a support sleeve is comparatively very expensive since materials such as nickel, steel or fiberglass-reinforced plastic are preferably used to achieve the required characteristics.